This invention relates to portable escape ladders, primarily for use as fire escape ladders, of the type which can be readily slung out from a building window and attached to the window ledge, or the like, to depend therefrom in the case of a fire or other emergency. Such ladders are well known and generally comprise a suspension bracket which grips over a window ledge, a pair of chains or like flexible suspension members attached each at one end to the bracket, a series of spaced, transverse ladder rungs slung between the chains and some form of stand-off means, if required, for holding the rungs a fixed distance from an outer wall surface when the ladder is in use.
One particular form of prior art ladder of the above type is shown in U.S. Pat. No. 3,834,492 to HUGO V. RONK and employs suspension chains depending from a window ledge-engaging bracket and tubular metal rungs slung between the chains. Connections between the suspension chains and the individual rungs are formed by flattening the ends of the rungs which are then notched and bent perpendicularly to the rung axis to form a hook-like member. The hook-like member is engaged in a chain link and then bent back against the rung about a line perpendicular to the longitudinal rung axis to trap the chain link in the notched section. Loads imposed on the rung in use, thereby act through the notched section of the flattened end which is of reduced cross-section and which has been subject to bending and thereby weakened.
It is an object of the present invention to provide a ladder of the above type which is simple and economical to manufacture while being strong and reliable in use.
More specifically it is an object of the invention, in a ladder of the above type, to provide a novel form of connection between each ladder rung and the suspension chains, which connections can be simply produced by conventional cold-forming processes performed on the rungs themselves, which connections includes no components additional to the rungs and chains and which connections are not subject to weaknesses imposed by cold working during the production of the connections.
It is a further object of the invention to provide for an escape ladder of the above type, a form of stand-off device which can readily and simply be attached to selected ladder rungs.